To the OP, why do you not just renew the SEP to your JAA licence, much easier to do. You are already SEP current enough by the sound of it.
It's just a basic skill test, no exams etc. SRG1157 refers. If you are in the midlands give me a shout and we can do it in a morning then no worries about mixing and matching.
You can take the licence down to Gatwick and they should renew the SEP while you wait if you are in a hurry or if its less than five years expired on the SEP I can sign the licence post test.